Narcotic analgesic agents, e.g., morphine, have excellent analgesic action against visceral pains or other, and are clinically used for alleviation of pain for terminal cancer patients. However, the narcotic analgesic agents are typical drugs that affect on mental functions and develop psychic and physical dependency. In addition, tolerance to analgesic action, as being their primary efficacy, is rapidly developed by repeated administrations. Accordingly, carefully controlled frequency of administration and dose are required to achieve a desired analgesic action, while maintaining minimized development of dependency.
Therefore, when a narcotic analgesic agent such as morphine is used, it is necessary to inhibit the development of tolerance to analgesic activity without reducing analgesic activity to meet the purpose of the use. It is also important to inhibit the development of dependency.
An object of the present invention is to provide a medicament having inhibitory activity against the development of dependency induced by the administration of the narcotic analgesic agent such as morphine. Another object of the present invention is to provide a medicament having inhibitory activity against the development of tolerance to analgesic action induced by the administration of the narcotic analgesic agent such as morphine. A further object of the present invention is to provide a medicament having both of the aforementioned pharmacological activities.